Laminated fabric

ABSTRACT

To provide a laminated fabric having an air permeability and a filtering capability, the laminated fabric includes a supporting layer and a protective layer bonded together. The protective layer includes a stretchable nonwoven fabric comprises an ultra-fine fiber. This laminated fabric has an air permeability of 2 cc/cm 2 /sec. or higher and a 1 μm quartz dust collecting efficiency of 90% or higher. The laminated fabric may also have a water resistant layer which is positioned on the protective layer so that the protective layer is employed as an intermediate layer between the water resistant layer and the supporting layer.

CROSS REFERENCE TO THE RELATED APPLICATIONS

This application is based on and claims Convention priority to Japaneseapplication No. 2007-066496, filed Mar. 15, 2007, the entire disclosureof which is herein incorporated by reference as a part of thisapplication.

FIELD OF THE INVENTION

The present invention relates to a laminated fabric (or a multi-layeredfabric) having a sufficient strength, an air permeability and afiltering capability, and more particularly, to the laminated fabric ofa kind capable of being easily reduced in volume at a low cost.

BACKGROUND ART

In order to protect human bodies from harmful and/or hazardoussubstances such as dust harmful to human bodies, contagions and viruses,and/or in order to avoid secondary infection resulting from infectedmediums having one or some of the hazardous substances adhering thereto,various protective materials are utilized. Such protective materials arerequired to have not only a filtering capability for effectivelyremoving the harmful and/or hazardous substances, but also an airpermeability to minimize the discomfort which the user may feel when theprotective material is brought into direct contact with the user's body.However, since the filtering capability and the air permeability areproperties incompatible with each other, and therefore, it is difficultto fulfill both the filtering capability and the air permeability at thesame time.

By way of example, Patent Document 1 listed below discloses a compositenonwoven fabric as a protective clothing material, which comprises anonwoven fabric having a water vapor permeability and a water proofingproperty, a porous fabric, and a thermally bondable nonwoven fabric. Inthe composite nonwoven fabric, the thermally bondable nonwoven fabric isinterposed between the water vapor permeable and water resistantnonwoven fabric and the porous fabric, and three of them are laminatedtogether. However, this conventional composite nonwoven fabric isincapable of being increased in air permeability as a composite nonwovenfabric in its entirety because the nonwoven fabric and the porous fabricare bonded to the thermally bondable nonwoven fabric which is distortedin a flexible film shape.

In addition, disposal of the protective materials contaminated withthose substances being harmful to human bodies has now come to be acontroversial issue. By way of example, the protective materials of thekind referred to above are generally utilized as a disposable materialand are heaped up as hazardous wastes in a plastic bag after one-timeuse. Then, the used protective materials are to be disposed of by wastedisposers. However, if the protective materials are bulky, such aproblem arises that increase in transportation cost as well as disposalcost of those protective materials, and therefore, demands have beenmade to reduce the costs by reducing the volume of those protectivematerials.

One way to reduce the volume of the protective materials may include amethod of reducing the pressure inside the bags or compressing thosebags, a method of reducing the volume of the bags by means of heatingsuch as dry heating or wet heating, and the like. But the method toreduce the volume by way of reduction of the pressure inside the bags isconsidered undesirable because it may emit contaminants to air beingexhausted.

Further, as one of the volume reduction methods by way of compression ofthe bags, there has been suggested an equipment designed to heat thecontaminated wastes so that the wastes can be caked in a block form tothereby reduce the volume, or an equipment designed to pulverize thewastes to thereby reduce the volume. Both of them are currentlyavailable in the commercial market, such equipments, however, areundesirable because of being extremely expensive and large in scale.Also, the reduction of the volume by means of the dry heat treatmentrequires heat resistant bags and is therefore costly to perform.

A method of and an apparatus for reducing the volume of infectiousmedical wastes by means of, for example, hot water has been suggested(See, for example, Patent Document 2 listed below.). Patent Document 2pertains to a method of and an apparatus for treating infectious medicalwastes, characterized in that a mixture of infectious medical wastes (A)which are made of a hydrophilic resin insoluble in a water having atemperature of not higher than 50° C., and water (B), which mixture hasa mixing ratio (A)/(B) of 70/30 to 20/80, is treated at a temperaturewithin the range of 70 to 150° C. so that the infectious medical wastes(A) can be solidified with their volume reduced. Although the apparatusdisclosed in Patent Document 2 appears to be compact in size, but hasrequired a special device to achieve the volume reduction.

[Patent Document 1] JP Laid-open Patent Publication No. 2003-336155

[Patent Document 2] JP Laid-open Patent Publication No. 2003-073498

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a laminated fabrichaving both of incompatible properties of air permeability and filteringcapability (collecting capability).

Another object of the present invention is to provide a laminated fabricwhich can be integrated without the air permeability being degraded.

A further object of the present invention is to provide a laminatedfabric which is effective to maintain the filtering capability evenafter it has been loaded.

A still further object of the present invention is to provide alaminated fabric, the volume of which can be reduced at a reduced costand without requiring the use of any special equipment.

As a result of intensive studies conducted by the inventors of thepresent invention in an attempt to accomplish those and other objects ofthe present invention, it has been found that if a laminated or layeredfabric is prepared by bonding a stretchable nonwoven fabric as aprotective layer to a supporting layer (or holding layer), the laminatedfabric can have both of the air permeability and the filteringcapability, which have hitherto been incompatible with each other, andcan hold the filtering capability even when some burden is placed on thelaminated fabric.

It has further been found that in the case where a volume reduciblesupporting layer (A layer) is used as the supporting layer and thevolume reducible supporting layer is prepared from fibers capable ofshrinking 5 to 90% when at least one layer is immersed in a hot water ofnot lower than 60° C.; the laminated fabric and a protective materialprepared therefrom can be obtained that can be readily reduced in volumeat a reduced cost without requiring the use of any special equipment.

In other words, the present invention provides a laminated fabric whichcomprises: a supporting layer; and a protective layer comprising astretchable nonwoven fabric formed from an ultra-fine fiber, theprotective layer bonded to the supporting layer; whereby the laminatedfabric having an air permeability of 2 cc/cm²/sec or higher and alsohaving an efficiency of 90% or higher when collecting quartz particles 1μm in size.

The ultra-fine fibers referred to above may comprise a thermoplasticelastomer, for example, a heat resistant thermoplastic elastomer. Thethermoplastic elastomer that can be employed in the practice of thepresent invention may comprise a thermoplastic elastomer selected fromthe group consisting of, for example, SEPS, SEBS, a polyurethane seriesthermoplastic elastomer, a polyester series thermoplastic elastomer anda polyamide series thermoplastic elastomer. The stretchable nonwovenfabric forming the protective layer may be of a kind having, forexample, a stretch of 30% or higher at break. This stretchable nonwovenfabric preferably comprises an ultra-fine fiber in the form of,particularly, a nanofiber having a fiber diameter within the range of 10to 1000 nm and also having a weight within the range of 0.01 to 10 g/m².

On the other hand, a part of the fibers forming the supporting layer maybe a volume reducible fiber. By way of example, the volume reduciblefibers may comprise a polyvinyl alcohol fiber. In other words, thepresent invention may encompass a laminated fabric having its volumecapable of being reduced with a hot water. Such a volume reduciblelaminated fabric may be of a kind capable of shrinking 5 to 90% whenimmersed in a hot water of 60° C. or higher.

Also, the laminated fabric of the present invention may include a waterresistant layer which is positioned on the protective layer so that theprotective layer is employed as an intermediate layer between the waterresistant layer and the supporting layer. In such case, the laminatedfabric may have a withstanding pressure within the range of about 300 to1500 mmH₂O.

Furthermore, the present invention also encompasses a protectivematerial, particularly, a protective clothing. The protective materialmay comprise the laminated fabric referred to above. Where the laminatedfabric has a volume reducing capability, the present invention alsoincludes a method of reducing the volume of the laminated fabric byplacing the laminated fabric into a sealable vessel and supplying a hotwater of 60° C. or higher to the laminated fabric.

As hereinabove discussed, the laminated fabric of the present inventioncan have the filtering capability and the air permeabilitysimultaneously when the laminated fabric comprises the supporting layerand the unique protective layer. In particular, since the protectivelayer has a stretchability, it can exhibit an excellent follow-upcharacteristic to any other layers. Accordingly, without the airpermeability being degraded, not only can the integrity of the laminatedfabric be improved, but the filtering capability of the laminated fabriccan be maintained even after a predetermined burden has been appliedthereto.

Specifically, where the nanofiber nonwoven fabric is used as theprotective layer, both a high air permeability and a high filteringcapability can be realized.

Also, where a volume reducible material is used as the supporting layer,the laminated fabric of the present invention can, after its volume hasbeen reduced with the use of hot water, be transported and/or disposedof easily and, therefore, the cost incurred in transportation and/ordisposal can be reduced advantageously.

BRIEF DESCRIPTION OF THE DRAWINGS

In any event, the present invention will become more clearly understoodfrom the following description of preferred embodiments thereof, whentaken in conjunction with the accompanying drawings. However, theembodiments and the drawings are given only for the purpose ofillustration and explanation, and are not to be taken as limiting thescope of the present invention in any way whatsoever, which scope is tobe determined by the appended claims. The drawings are not necessarilyto scale, and emphasis has instead been placed upon illustrating theprinciples of the invention. In the accompanying drawings, likereference numerals are used to denote like parts throughout the severalviews, and:

FIG. 1 is a schematic diagram of an apparatus for manufacturing aprotective layer which is a nanofiber layer containing tangled anddeposited nanofibers, showing an example of a laminated fabric accordingto a preferred embodiment of the present invention; and

FIG. 2 is a schematic sectional view showing an example of the structureof the laminated fabric (a laminate) according to a preferred embodimentof the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The laminated fabric of the present invention is a laminated fabric(layered fabric) of a structure having a protective layer and asupporting layer bonded together, in which the protective layer includesa stretchable nonwoven fabric prepared from ultra-fine fibers. Thelaminated fabric of the present invention has an air permeability of 2cc/cm²/sec. or higher and also has an efficiency of 90% or higher whencollecting quartz particles 1 μm in size.

[Supporting Layer]

The supporting layer employed in the laminated fabric of the presentinvention is provided for the purpose of retaining the protective layer.The supporting layer may not be specifically limited to a particularone, as long as the laminated fabric as a whole can exhibit a specificair permeability. The supporting layer may be employed in the form of awoven fabric, a knitted fabric, or a nonwoven fabric.

The supporting layer referred to above may be prepared from eithernatural fibers such as, for example, animal or vegetable fibers, orvarious synthetic fibers, depending on the purpose of use of thelaminated fabric. Those fibers may be employed singly or in combination.

The synthetic fibers used to form the supporting layer may be polyvinylalcohol fibers; ethylene-vinyl alcohol fibers; polyamide fibers(including, for example, aliphatic polyamide fibers comprising, forexample, nylon 6, nylon 66, nylon 46, nylon 610, nylon 11 and/or nylon12, alicyclic polyamide fibers, aromatic polyamide fibers such as aramidfibers, and semi-aromatic polyamide fibers consisting of an aromaticdicarboxylic acid and an aliphatic alkylenediamine); polyolefinic fibers(including, for example, polyethylene fibers, polypropylene fibers andcomposite fibers of polypropylene and polyethylene); polyester fibers(including, for example, polyethylene terephthalate fibers); acrylicfibers (including, for example, polyacrylonitrile fibers and polymethylmethacrylate fibers); polyurethane fibers; cellulose fibers (including,for example, rayon fibers and acetate fibers); halogen-containing fibers(including, for example, vinyl chloride fibers, vinylidene chloridefibers, polyvinyl fluoride fibers, polyvinylidene fluoride fibers andfibers made of a copolymer of polyvinylidene fluoride andhexafluoropropylene); polyimide fibers; polybenzimidazole fibers;polyarylate fibers; or polyphenylene sulfide fibers.

Of those fibers enumerated above, the polyvinyl alcohol fibers, theethylene vinyl alcohol fibers, the polyamide fibers or the polyesterfibers are preferred as a material for the synthetic fibers employed inthe supporting layer.

The fineness of the fibers forming the supporting layer may be of anyvalue that can be chosen as desired depending on the texture or feelingwhich is required to the laminated fabric, but may be within the rangeof, for example, about 0.1 to 1000 dtex, and preferably within the rangeof about 1 to 400 dtex. Also, where the supporting layer is a wovenfabric, warps and wefts of the woven fabric may have respectivefinenesses, which may be either the same or different from each other,but the ratio of the fineness of the wefts relative to the fineness ofthe wasp (i.e., the warp fineness/weft fineness) may be within the rangeof about 10/1 to 1/10, and preferably within the range of about 5/1 to1/5.

The weight of the supporting layer per unit area may be of any valuethat can be chosen as desired depending on the form of the supportinglayer, and not specifically limited to a particular value so long as theair permeability and the collecting capability both required in thepractice of the present invention are satisfied. The weight of thesupporting layer per square meter may be within the range of about 5 to100 g/m² and, preferably, within the range of about 10 to 90 g/m².

The supporting layer may be in the form of a woven fabric, a knittedfabric, a nonwoven fabric or a synthetic paper, and may not bespecifically limited to a particular form as long as the eventuallyformed laminated fabric can have a predetermined or required airpermeability and collecting capability. In any event, the woven fabric,the knitted fabric, the nonwoven fabric or the synthetic resin referredto above may be prepared in any known or customarily practiced method.

Of the various forms of the supporting layer, the nonwoven fabric ispreferred for the supporting layer in terms of the collecting capabilityand the air permeability.

The method of making the supporting layer using the nonwoven fabric isnot specifically limited to a particular method, and any of a spunbonding method, a meltblown method, a spun lacing method, a thermalbonding method, a chemical bonding method, an airlaid method and aneedle punching method can be employed therefor.

(Volume Reducible Supporting Layer)

Further, in terms of the volume reducing capability, the supportinglayer of the present invention, may be a volume reducible supportinglayer (A layer) prepared from fibers capable of shrinking 5 to 90% afterimmersion of the fibers in a hot water of 60° C. or higher. In otherwords, when the laminated fabric of the present invention is used underthe working environment of 50° C. or lower, the laminated fabric canexhibit a satisfactory protective function against dust, contagionsand/or viruses without shrinking due to moisture such as sweat. On thecontrary, at the time it is desired to be disposed of, the laminatedfabric is immersed in a hot water of 60° C. or higher, and the shrinkageof a portion of the fibers forming the laminated fabric results inreduction of the laminated fabric entirely in volume.

Where such a feature as discussed above is possessed in the laminatedfabric of the present invention, even if a layer (B layer) incapable ofundergoing shrinkage in a water of 50° C. or lower is used, when the Blayer is bonded to the volume reducible supporting layer (A layer)prepared from the fibers capable of undergo 5 to 90% shrinkage whenimmersed in the hot water of 60° C. or higher, the resultant protectivelaminated fabric as well as a protective clothing prepared therefromwill have an excellent volume reducing capability as will be discussedin detail later.

In the practice of the present invention, in order to reduce the volumeof the laminated fabric for a protective clothing on the whole, at leasta part of the fibers forming the supporting layer may be a volumereducible fiber capable of undergoing shrinkage when immersed in a hotwater.

The volume reducible fibers referred to above are preferably hydrophilicfibers, more specifically, fibers of a water soluble synthetic polymer,and particularly PVA (polyvinyl alcohol) fibers comprising a vinylalcohol polymer. The PVA fiber has a biodegradability and is, therefore,excellent in terms of low impacts on the environments during undergrounddisposal.

The kind of vinyl alcohol polymers used for the PVA fibers that can besuitably employed in the A layer in accordance with the presentinvention may not be specifically limited to a particular type, and thepreferred vinyl alcohol polymers may be the one having aviscosity-average degree of polymerization of 1,000 or higher, andparticularly 1,500 or higher in terms of the practical mechanicalperformance; or 5,000 or lower in terms of the spinning capability andcost. Also, by the same reason, the preferred vinyl alcohol polymers maybe the one having a degree of saponification of 50 mole % or higher,preferably 65 mole % or higher and, more preferably 80 mole % or higher.

The vinyl alcohol polymer may be copolymerized with any other monomer,and the examples of a copolymerizing component include ethylene, vinylacetate, itaconic acid, vinyl amine, acrylamide, vinyl pivalate, maleicanhydride, a sulfonic acid-containing vinyl compound, and the like.

In terms of the practice mechanical performance, the vinyl alcoholpolymer preferably contains a vinyl alcohol unit in a quantity of 70mole % or higher of the total constituent unit. Also, so long as theeffects of the present invention are not lost, the fibers may containone or more polymers, other than the vinyl alcohol polymer, and anyadditive(s). In terms of the fiber performance, the content of the vinylalcohol polymer preferably exceeds 30 mass % per fibers and, morepreferably 50 mass % per fibers.

There will now be described a method of making the PVA fibers, which canbe suitably employed in the A layer in accordance with the presentinvention. When the fibers are prepared with a spinning liquid in whicha water soluble PVA polymer is dissolved in water or an organic solventby a method as will be described later, the fiber excellent inmechanical characteristics can be efficiently manufactured.Nevertheless, so long as the effects of the present invention are notlost, the spinning liquid may contain one or more additives and anyother polymer. The solvent forming a part of the spinning liquidincludes, for example, water; a polar solvent such as dimethylsulfoxide(DMSO), dimethylacetamide, dimethylformamide or N-methylpyrrolidone; apolyvalent alcohol such as glycerin or ethylene glycol; a mixture of oneof those solvents with a swellable metal salt such as rhodan salt,lithium chloride, calcium chloride or zinc chloride; a mixture of thosesolvents; or a mixture of one of those solvents with water. Among thosesolvents, water or DMSO is most preferred in terms of the solubility ata low temperature, low toxicity and low corrosive properties.

The concentration of the polymer contained in the spinning liquid mayvary depending on the liquid components, the degree of polymerization orthe solvent to be used, and is preferably within the range of 8 to 40weight percent. The liquid temperature of the spinning liquid at thetime of extrusion is within a range enough to avoid gelling, decomposingand coloring of the spinning liquid, and is specifically preferablywithin the range of 50 to 150° C.

The above-mentioned spinning liquid can be suitably allowed to subjectto a wet spinning, a dry spinning or a dry-jet wet spinning afterextruding of the spinning liquid from a nozzle, and the spinning liquidmay be extruded into a coagulating bath capable of solidifying the PVApolymer. In particular, where the spinning liquid is extruded throughmultiple holes, the use of the wet spinning process is preferred ratherthan the dry-jet wet spinning process because conglutination of thefibers can be avoided during the extrusion of the spinning liquid. It isto be noted that the wet spinning process referred to above is aprocess, in which the spinning liquid can be extruded from a nozzledirectly into a coagulating bath (solidifying bath), whereas the dry-jetwet spinning process is a process, in which the spinning liquid is firstextruded from a nozzle into the atmosphere full of air or inert gas andthen introduced into a coagulating bath.

The coagulating liquid used in the practice of the present inventionvaries depending on whether the solvent in the spinning liquid is anorganic solvent or whether it is water. In the case of the spinningliquid utilizing the organic solvent, the use is preferred of a mixedliquid containing the coagulating liquid and the spinning liquid solventin order to improve the eventually obtained fiber strength or the like.The coagulating liquid used in the mixed solution may be an organicsolvent such as an alcohol (including, for example, methanol andethanol), or a ketone (including, for example, acetone and methyl ethylketone), which solvent is of a kind having a solidifying capability tothe PVA polymer. In particular, an organic solvent containing methanoland DMSO is preferred, which are preferably mixed in a mixing ratio(methanol)/(DMSO) of 55/45 to 80/20 in terms of the productivity and thesolvent recovery. Also, the temperature of the coagulating liquid ispreferably 30° C. or lower, and particularly for achieving a uniformgelatinization upon cooling, it is preferably 20° C. or lower, and morepreferably 15° C. or lower. On the other hand, in the case where thespinning liquid is used in the form of an aqueous solution, thecoagulating bath includes an aqueous solution of mineral salts having asolidifying capability to the PVA polymer. For example, mirabilite,sodium chloride or carbon hydrate can be suitably employed for thesolidifying solvent forming a part of the coagulating liquid. As amatter of course, the coagulating liquid referred to above may be eitheracidic or alkaline.

Thereafter, the solvent in the spinning liquid is removed by extractionfrom extruded filaments to solidify the filaments. It is preferred thatthe filaments can be stretched in the bath during the extraction step,not only because conglutination of the fibers during drying can besuppressed, but also because the eventually obtained fibers can have anincreased strength. The degree of stretching is preferably within therange of 1.5 to 6 times. The extraction of the solvent is carried outgenerally by passing the extruded filaments through a plurality ofextraction baths. For the extraction baths, the coagulating liquidsingly or a mixture of the coagulating liquid with the solvent for thespinning liquid can be employed, and the extraction baths may have atemperature within the range of 0 to 80° C.

Then, the filaments are dried to obtain PVA fibers. At this time, anoiling agent may be applied as required during the drying process. Thedrying temperature is preferably 210° C. or lower. In particular, theuse of a multi-stage drying is preferred, which may be carried out insuch a manner that the drying is performed at a temperature equal to orlower than 160° C. at the initial stage of drying, and at the laterstage of drying, the drying is performed at a higher temperature.Further, a dry heat stretching and, if required a dry heat shrinking,are preferably carried out to orient and crystallize PVA molecularchains to thereby increase the tenacity of the fibers. When the fibersare used to form structures such as nonwoven fabrics, if the tenacity ofthe fibers is too low, reduction in in-process transportability may bereadily expected. In order to increase the mechanical performance of thefibers, the dry heat stretching is preferably carried out under atemperature condition within the range of 120 to 280° C.

The fineness of the PVA fibers that can be obtained by the manufacturingmethod described hereinabove is not specifically limited to a particularvalue, and the PVA fibers may have a fineness selected from a largerange, for example, within the range of 0.1 to 1,000 dtex, andpreferably 1 to 400 dtex. The fineness of the fibers may be suitablyadjusted depending on the diameter of the nozzle and/or the stretchingratio. Also, the fibers may have a length which is not specificallylimited to a particular value, and may be suitably selected inconsideration of the purpose of use.

It is to be noted that the fibers that can undergo 5 to 90% shrinkagewhen immersed in a hot water of a temperature equal to or higher than60° C. may be employed as a part of the A layer, not necessarilyemployed in the entirety of the A layer. Where a part of the A layercomprises those shrinkable fibers capable of undergoing 5 to 90%shrinkage when immersed in the hot water of 60° C. or higher, theshrinkage percentage may be lowered as compared with the case, in whichthe A layer in its entirety is prepared from the shrinkable fibers.However, even if only a part of the A layer comprises those shrinkablefibers; the laminated fabric in its entirety can be shrunken 5 to 90%when the material and the composition ratio are suitably selected.

[Protective Layer]

The protective layer employed in the laminated fabric of the presentinvention includes a stretchable nonwoven fabric prepared fromultra-fine fibers in terms of the capability of collectingmicroparticles. The stretchable nonwoven fabric substantially retains afibrous shape as a nonwoven fabric, without being transformed into afilm in the laminated fabric, for the purpose of securing the airpermeability. For this reason, while the laminated fabric of the presentinvention has a high filtering performance enough to have an efficiencyof 90% or higher when collecting quarts particles of 1 μm in size, italso ensures an air permeability as high as 2 cc/cm²/sec concurrently.Also, since the protective layer has a stretchability, it can exhibit agood follow-up characteristic with both the supporting layer and a waterresistant layer as will be described later. Accordingly, when thelaminate fabric is used for wearing as a protective clothing, theprotective layer will hardly break. Accordingly, reduction in filteringcapability of the laminated fabric as a whole can be suppressedadvantageously, even when a predetermined loading such as stretching isimposed on the laminated fabric.

The ultra-fine fibers employed in the practice of the present inventionmay not be specifically limited to a particular type as long as itprovides stretchability to the non-woven fabric. The frequently employedultra-fine fibers are formed from a thermoplastic elastomer in view ofthe elasticity and fiber forming properties.

Examples of the thermoplastic elastomer includes a styrene seriesthermoplastic elastomer, a urethane series thermoplastic elastomer, anolefinic thermoplastic elastomer, a vinyl chloride series thermoplasticelastomer, a polyester series thermoplastic elastomer, a polyamideseries thermoplastic elastomer, and the like. Those thermoplasticelastomers may be employed singly or in combination. Also, thethermoplastic elastomer referred to above may be a polymer blend ofthermoplastic elastomer, in which the thermoplastic elastomer iscombined with a polymer material for the synthetic fibers (for example,olefinic polymers) discussed previously under the heading of thesupporting layer. In addition, if required, one or more kind of organicor inorganic powders may be mixed in the thermoplastic elastomerreferred to above.

The urethane series thermoplastic elastomer comprises a hard segmentcomprising a low molecular weight glycol and a diisocyanate, and a softsegment comprising a high molecular weight diol and diisocyanate.

The low molecular weight glycol includes, for example, C1-10 diols suchas ethylene glycol, 1,4-butane diol and 1,6-hexane diol, whereas thehigh molecular weight diol includes, for example, poly(1,4-butyleneadipate, poly(1,6-hexane adipate), polycaprolactone, polyethyleneglycol, polypropylene glycol and polyoxytetramethylene glycol. Thediisocyanate referred to above includes, for example, tolylenediisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylenediisocyanate and isophorone diisocyanate.

The styrene series thermoplastic elastomer includes, for example, SBS(styrene/butadiene/styrene block copolymer), SIS(styrene/isoprene/styrene block copolymer), SEBS(styrene/ethylene/butadiene/styrene block copolymer) and SEPS(styrene/ethylene/propylene/styrene block copolymer).

The olefinic thermoplastic elastomer comprises a polyethylene or apolypropylene as a hard segment and SEBS or an ethylene/propylenecopolymer as a soft segment.

The vinyl chloride series thermoplastic elastomer comprises acrystalline polyvinyl chloride as a hard segment and a non-crystallinepolyvinyl chloride or acrylonitrile as a soft segment.

The polyester series thermoplastic elastomer comprises a saturatedpolyester as a hard segment and an aliphatic polyether or aliphaticpolyester as a soft segment.

The polyamide series thermoplastic elastomer comprises a polyamide as ahard segment and, as a soft segment, a polyester or a polyether that isnon-crystalline and has a low glass transition temperature.

Of those thermoplastic elastomers referred to above, SEPS, SEBS, theurethane series thermoplastic elastomer, the polyester seriesthermoplastic elastomer or the polyamide series thermoplastic elastomercan be advantageously employed in terms of the heat resistance.

This kind of the heat resistant and stretchable nonwoven fabric does nottransform into a film even when the protective layer and the supportinglayer are integrated together by means of a thermo compression bondingto form the laminated fabric, and, therefore, a predetermined airpermeability can be secured in the laminated fabric.

It is to be noted that if the supporting layer is a volume reduciblesupporting layer (A layer) capable of undergoing shrinkage when immersedin a hot water, such a supporting layer may be bonded to a layer (Blayer) of a kind, which does not undergo shrinkage in a water having atemperature of not higher than 50° C., to provide a laminated fabric,and the resultant laminated fabric will be a volume reducible laminatedfabric capable of undergoing shrinkage in a hot water of a temperatureequal to or higher than 60° C.

In such case, the fabric material, the weight and the thickness of the Blayer may not be specifically limited to a particular one or particularvalues and may be arbitrarily chosen in consideration of an object to beprotected, but the B layer preferably has a water resistance sufficientto substantially avoid shrinkage in contact with a moisture componentsuch as, for example, sweats when it is used under the workingenvironment of 50° C. or lower.

The ultra-fine fibers forming the stretchable nonwoven fabric referredto above has an average fiber diameter preferably not greater than, forexample, 10 μm (for example, within the range of about 10 nm to about 8μm), and more preferably not greater than 5 μm because the eventuallyformed laminated fabric has both the air permeability and the filteringcapability. The ultra-fine fibers of this kind can be prepared in anyknown manner such as a meltblown process.

Specifically, in view of the necessity to increase the air permeabilityand the protecting capability, the ultra-fine fibers employed in thepractice of the present invention may be nanofibers having an averagefiber diameter within the range of 10 to 1,000 nm (preferably within therange of about 15 to 800 nm and, more preferably, within the range ofabout 25 to 600 nm).

In order to strike a delicate balance between the protecting capabilityand the air permeability of the laminate fabric, the important pointshould be how the pressure loss of the fabric is minimized and howharmful microparticles can be collected by the fabric. In view of theabove point, the nanofibers are considered to be suitable from theviewpoint of striking a balance between the protecting capability andthe air permeability partly because they can exhibit the Slip Floweffect enough to reduce the pressure loss during the filtration andpartly because they have a high air permeability. (Takeyuki Kawaguchi,“Kodo Sangyo Hakkutsu Senryaku (Strategy of Advanced IndustrialStructure Development Using Nanofiber Technology)” (Supervising Editor:Tatsuya Motomiya), Chapter 10, pp. 373)

It is to be noted that the fiber diameter herein referred to inconnection with the present invention means a diameter of the transversesection of fibers that can be measured from an electron micrograph takenof a fiber aggregation at a magnification of ×5,000, and is an averagevalue obtained by measuring the fiber diameters of randomly chosen 50fibers.

The weight of the stretchable nonwoven fabric per unit area employed inthe practice of the present invention is not specifically limited to aparticular value as long as the laminated fabric of the presentinvention satisfies the air permeability and the collecting ability bothdefined in the present invention, but may be chosen in consideration ofthe average fiber diameter of the ultra-fine fibers.

By way of example, in the case where the average fiber diameter of theultra-fine fibers exceeds 1 μm, the weight of the stretchable nonwovenfabric is preferably within the range of about 1 to 20 g/m², and morepreferably within the range of about 5 to 15 g/m².

Also, by way of example, if the average fiber diameter of the ultra-finefibers is not greater than 1 μm, the weight of the stretchable nonwovenfabric is preferably within the range of about 0.01 to 10 g/m², morepreferably within the range of about 0.03 to 8 g/m², and furtherpreferably within the range of about 0.05 to 6 g/m².

If the weight of the non-woven fabric is too large for the average fiberdiameter, it may occur that the air permeability discussed previouslywill be lowered below 2 cc/cm²/sec. although the laminate fabric has animproved protecting capability from passage of microparticles such as,for example, asbestos hazardous to the human body. In particular, in thecase of the nanofibers, increase in cost will occur with an increasedproportion to the nanofibers in the fabric, and therefore, it is notpreferable. On the other hand, if the weight of the non-woven fabric istoo small, the air permeability will improve, but it is not preferablebecause it would be difficult to uniformly distribute over the entiresupporting layer, and as a result, the efficiency of collecting the 1 μmquartz particles will be lowered below 90%.

Since the protective layer comprises the stretchable nonwoven fabric ashereinabove described, it is possible to increase the stretch at break(%) as compared with the non-stretchable nonwoven fabric. By way ofexample, the stretch (%) of the stretchable nonwoven fabric at break maybe of a value equal to or higher than, for example, 30% (for example,within the range of about 30 to 200%) and, preferably, within the rangeof about 35 to 180%, when an oblong test piece thereof having a width of15 mm is measured in accordance with JIS P8113.

The stretchable nonwoven fabric can be prepared by the method of makingthe nonwoven fabric, described hereinbefore under the heading of thesupporting layer, using ultra-fine fibers. Also, in the case of theultra-fine fibers being nanofibers, the nonwoven fabric prepared fromthe nanofibers may be manufactured by the use of the following process.

In the first place, the nanofibers referred to above may be prepared bythe use of, for example, the following method. As a polymer spinningliquid (or spinning liquid), either a dissolved polymer solution inwhich a polymer is dissolved in a solvent capable of dissolving suchpolymer, or a melted polymer solution in which the polymer is melted byheating, can be suitably employed. Then, nanofibers are laminated orconjugated as the previously described B layer by means of anelectrostatic spinning process using the spinning liquid. For theelectrostatic spinning process, a method can be employed, in which whilea high voltage is applied to an electroconductive member capable ofdispensing the spinning liquid, nanofibers can be deposited on a counterelectroconductive member (or electrode) that is grounded to the earth.By this method, the spinning liquid that is extruded from a spinningliquid supply unit can be electrified (or charged) to split the dropletsfrom the spinning liquid; fibers are then continuously drawn from onepoint of the liquid droplets under the influence of an electric field;and the split and divided fibers are diffused, and finally beingdeposited on a collecting belt or sheet disposed at a location spaced afew to tens centimeters from the spinning liquid supply unit. The fibersare slightly conglutinated simultaneously with deposition to inhibitmovement of those fibers and a dense sheet can be obtained whenultra-fine fibers are successively deposited on the moving collectingbelt or sheet.

In other words, referring to FIG. 1, the spinning liquid in which thepolymer is dissolved is measured and transmitted by a metering pump 1,and is distributed under a uniform pressure and flow by a distributingand rectifying block 2. Then the distributed spinning liquid is suppliedto a nozzle unit 3. The nozzle unit 3 has spinnerets 4 each fittedthereto so as to protrude the spinnerets 4 having a respective hole of ahollow needle configuration, and leakage of electricity over the nozzleunit 3 is prevented by electrically insulating members 5. The protrudingspinnerets 4, each made of an electroconductive material, are fitted tothe nozzle unit 3 so as to be vertically downwardly oriented andjuxtaposed relative to each other in a direction perpendicular to thedirection of travel of a sheet take-up apparatus 7, which may be in theform of an endless conveyor. An output terminal of a high voltage DCgenerating unit is fitted to each of the projecting spinnerets 4 so thatapplication to those spinnerets 4 can be made possible through aconducting wire. The endless conveyor in the sheet take-up apparatus 7has a grounded electroconductive member 8 fitted thereto so that theapplied potential can be neutralized. The spinning liquid supplied underpressure from the nozzle unit 3 to the projecting spinnerets 4 iselectrified to split, fibers are then continuously drawn from one pointof liquid droplets under the influence of an electric field, and thenthe nanofiber scaffolds deposited on the electroconductive member fittedto the sheet take-up apparatus 7. The deposited nanofibers, in whichslight conglutination proceeds, are moved with the movement of the sheettake-up apparatus 7, and simultaneously with the movement of the endlessconveyor, another deposition ejected from the spinnerets 4 is placedonto the next to the former deposition in the endless conveyor. As aresult, a dense and uniform sheeting can be formed by repeatingdeposition of ultra-fine fibers.

[Laminated Fabric]

The laminated fabric comprises the protective layer and the supportinglayer which are bonded together. The method of bonding the supportinglayer and the protective layer together to provide the laminated fabricmay not be specifically limited to a particular one. By way of example,where the nonwoven fabric is used, thermal bonding, chemical bonding,needle punching, hydroentangling or any other method can be suitablyemployed. Also, coating of the protective layer to the supporting layerby means of a method such as, for example, spun bonding, meltblowing,and electro-spinning may be suitably employed with no problem.

Also, where no affinity exists between the supporting layer and theprotective layer, a bonding layer (for example, a layer to be used forbonding with a binder or for bonding resulting from thermal fusion)having an affinity to respective compositions of those layers may beinserted in between those layers. For example, where a thermally fusiblebonding layer is employed therebetween, the relationship between thesoftening point (TB) of the fibers forming the stretchable nonwovenfabric (the protective layer) and the softening point (TH) of thethermally fusible bonding layer may be TH<TB, preferably about TH+5≦TBand more preferably about TH+10≦TB.

Also, in the practice of the present invention, in order to increase thewater resistance of the laminated fabric, a water resistant layer may befurther positioned or laminated on the protective layer so that theprotective layer is employed as an intermediate layer between the waterresistant layer and the supporting layer. The use of the water resistantlayer so laminated is effective to inhibit the reduction of thecollecting capability and the air permeability of the protective layerresulting from deposition of water components, even when the laminatedfabric is used under high humidity or under the environment susceptibleto deposition of the water components.

For example, as the water resistant layer, a moisture permeable andwater resistant nonwoven fabric may be employed. The moisture permeableand water resistant nonwoven fabric referred to above can be formed byapplying a water repellent or water resistant coating to the nonwovenfabric formed by the use of the various fibers previously discussedunder the heading of the supporting layer, but in terms of securement ofthe air permeability of the supporting layer, the water resistant layeris preferably formed with hydrophobic fibers. The hydrophobic fibers maybe exemplified with polyolefinic fibers or polyester series fibers, bothof which have been discussed previously under the heading of thesupporting layer, and two of them, the polyolefinic fibers are preferredtherefor. As a process of laminating the water resistant layer, any ofthe method discussed under the method of laminating the supporting layerand the protective layer together can be employed. The water resistantlayer has a weight, which may be so chosen as to be within the range of,for example, about 5 to 50 g/m² and, preferably, within the range ofabout 10 to 45 g/m² in order to impart water resistant property.

Also, in the laminated fabric, the total of the respective weights ofthe supporting and protective layers (plus that of the water resistantlayer that is employed if desired) may be arbitrarily chosen dependingon the characteristics of the supporting layer and/or those of theprotective layer and may be within the range of, for example, about 30to 100 g/m² and, preferably within the range of about 40 to 90 g/m².

Specifically, in the case where the supporting layer has a volumereducing capability in view of reducing the volume of laminate fabric inits entirety, the thickness of the protective layer (plus the thicknessof the water resistant layer that is employed if desired) relative tothe thickness of the supporting layer may be not larger than about twiceof the thickness of the supporting layer, and preferably not larger thanabout 1.5 times the thickness of the supporting layer.

It is to be noted that if required, a film may be bonded to a part ofthe supporting layer. Even in such case, a method of bonding the film tothe fibers may not specifically limited, but such bonding may beaccomplished by means of the use of a binder or a thermal fusion.

Also, if required, in order for the resultant sheeting comprising thefilm to be utilizable in any of various applications, any post-treatmentmay be performed. By way of example, a calendering treatment fordensification, a treatment to impart a hydrophilic property, a waterrepellent treatment, and/or a surfactant depositing treatment may beperformed.

The laminated fabric for a protective clothing according to the presentinvention is preferably subjected to an electret treatment. The electrettreatment referred to above means a material capable of semipermanentlyretaining electric polarization even in the absence of any externalelectric field and forming an electric field in the surrounding, and theelectret treatment can be performed with an easily chargeable materialsuch as, for example, a polypropylene.

That is because since when the electret treatment is performed, acollecting function by means of the electrostatic force can be added,the efficiency of collecting the microparticles can be drasticallyincreased without altering the air permeability. With respect to theelectret treatment, various systems such as, for example, a thermalelectret, an electroelectret, a photoelectret, a radioelectret, amagnetelectret, a mechanoelectret are available, and any of them can besuitably employed.

In terms of the protecting capability, the laminated fabric manufacturedin the manner described hereinabove has an efficiency of 90% or higher,preferably 93% or higher, and more preferably 96% or higher, whencollecting quartz particles 1 μm in size.

Dust particles, contagions and viruses, all harmful to human bodies,have varying particle sizes. Asbestos, which are an exemplary harmfuldust, are made up of an aggregation of fibrous matters of a lengthwithin the range of a few μm to some tens μm. The sizes of bacteria andfungi, which are a kind of contagions, are 2 to 3 μm in most cases.Although viruses themselves have sizes of 0.01 to 0.1 μm, the route ofinfection is in most cases by way of a droplet infection caused bypatients' coughing, and the sizes of the droplets are 2 μm or greater inmost cases. Considering the above mentioned sizes, it can be expectedthat if the efficiency of collecting the 1 μm quarts particles is 90% orhigher, those dusts, contagions and viruses can be substantially almostcompletely protected.

On the other hand, if the efficiency of collecting the 1 μm quartzparticles is lower than 90%, it is indeed undesirable in terms of theprotecting capability discussed above.

The laminated fabric of the present invention has an air permeability of2 cc/cm²/sec. or higher in order to secure an amenity to the human body.If the air permeability is lower than 2 cc/cm²/sec., one will feeluncomfortable with humid and, therefore, it is not desirable. The airpermeability of the laminated fabric is preferably not lower than 3cc/cm²/sec. and more preferably within the range of 3.5 cc/cm²/sec. to10 cc/cm²/sec. As for the relationship between the air permeability andthe 1 μm quartz particle collecting efficiency discussed previously,increase of the protecting capability lowers the air permeability,accompanied by increase of the humidity. As a result, the usagecharacteristics, for example, the amenity of wearing will be lowered. Inorder to prevent such an undesirable result, the protecting capabilityand the air permeability are desired to fall within the respectiveranges of performance discussed hereinbefore.

In the present invention, since the stretchable nonwoven fabric is usedfor the protective layer, the follow-up characteristic of the protectivelayer with any other layers, that is, the supporting layer or theprotective layer is excellent. Accordingly, even after a predeterminedloading has been imposed, it is possible to keep the integrity of thelaminated fabric as a whole, and any undesirable reduction in filteringcapability can also be avoided. The laminated fabric of the presentinvention, even when being washed five times and dried in a manneraccording to, for example, the JIS L1096 B.23.1 A method, may have a 1μm quarts particle collecting efficiency of 90% or higher (preferably93% or higher and, more preferably, 95% or higher).

If the laminated fabric has a water resistance, the withstandingpressure of the laminated fabric, when measured according to a low waterpressure method stipulated in JIS L1092 may be within the range of about300 to 1,500 mmH₂O, and preferably within the range of 400 to 1,000mmH₂O. If the withstanding pressure is too low, it will not play a roleof protecting the protective layer from water, but if the withstandingpressure is too high, there is a possibility that the laminated fabricas a whole will have an air permeability departing from thepredetermined value.

Also, where the laminated fabric has a volume reducing capability, thevolume reducible laminated fabric may undergo about 5 to 90% shrinkagein a hot water of 60° C. or higher (for example, 60° C. or higher, butlower than 70° C.), and when a disposal space is considered, it mayundergo about 10 to 92% shrinkage, and preferably about 20 to 94%shrinkage. In particular, in terms of increase in the rate of shrinkage,the laminated fabric may undergo 30 to 95% shrinkage and, preferably 40to 90% shrinkage when held in a hot water of 70° C. or higher (forexample, 70° C. or higher, but lower than 80° C.).

It is to be noted that the rate of shrinkage herein referred to means avalue calculated according to the method described later under theheading of the rate of shrinkage (%) of the fabric in a hot water.

[Method of Reducing the Volume of Volume Reducible Laminated Fabric]

Where the laminated fabric of the present invention has a volumereducing capability, the volume of the laminated fabric can easily bereduced with no use to any special equipment and at a reduced cost.

By way of example, reduction in volume of the laminated fabric can beaccomplished by putting the volume reducible laminated fabric (and theprotective material prepared form such fabric) into a suitable vessel(for example, a plastic container or a plastic bag) and supplying a hotwater of 60° C. or higher to the laminated fabric. A method of supplyingthe hot water is not particularly limited to a specific method, and thehot water may be filled in the vessel before the laminated fabric is puttherein; or after water is filled in a sealable vessel, such water maybe heated to a predetermined temperature in the vessel.

For example, for heating, any suitable method may be employed, as longas the water within the vessel can be heated to a temperature equal toor higher than 60° C. There may be suitably employed for this purpose,for example, a method of applying a hot air from the outside of thevessel, a method of immersing the vessel itself into a hot water, or amethod of heating water in the vessel by the means of an inductionheating apparatus such as, for example, an electronic oven.

The proportion of the hot water relative to the laminated fabric is notspecifically limited to a particular value as long as the volume of thelaminated fabric can be reduced, and relative to 100 parts by weight ofthe laminated fabric, 200 parts by weight or larger (for example, withinthe range of about 250 to 500 parts by weight), and preferably 300 partsby weight or larger (for example, within the range of about 350 to 450parts by weight) of the hot water may be employed.

Where the vessel used to achieve the volume reduction is employed in theform of a plastic bag, reduction of the volume of the protectiveclothing can be achieved by putting 200 parts by weight or larger ofwater relative to 100 parts by weight of the laminated fabricconstituting the protective clothing into the plastic bag; sealing theplastic bag; and then heating the plastic bag from the outside of thebag with a heater or heating the inside of the bag by means of aninduction heating apparatus such as, for example, an electronic oven, tothereby reduce the volume of the protective clothing. The plastic bagreferred to herein may not be particularly limited to a specific one aslong as it will be neither melted or decomposed at a temperature of usethereof, and may be of a kind having a moisture resistance and a waterresistance effective to avoid leakage of water.

It is to be noted that a method of sealing the plastic bag may also notbe specifically limited to a particular method, and any of a method oftightly tying itself, a method of closing the mouth of the bag with theuse of a fastening tool and a method of heat sealing the bag may beemployed.

The protective clothing utilizing the volume reducible laminated fabriccan be transported or disposed of after the volume thereof has beenreduced subsequent after use. As a result, the cost, which will beincurred in transportation and disposal, can be reduced advantageously.

Hereinafter, the present invention will be demonstrated by way ofexamples and comparative examples, which are not intended to limit thescope of the present invention, but are only for illustrative purpose.

[Shrinkage Rate of Fabric in Hot Water (%)]

The fabric is cut into a sample of 10×10 cm in size, which sample isthen immersed for 2 minutes in a hot water in a free state. After theimmersion, the fabric is removed from the hot water and the removedfabric is drained off lightly. Then respective dimensions (cm) of thefabric in a longitudinal direction (X) and a transverse direction (Y)are measured so that the rate of shrinkage can be calculated by thefollowing equation:

Shrinkage Rate(%)={[(10−X)/10]+[(10−Y)/10]}/2×100

[Dust Collecting Efficiency (%)]

In accordance with the testing for particulate respirators stipulated inJIS T8151, the dust collecting efficiency was measured using a “MaskTester: Model AP-6310FP” manufactured by and available from ShibataScientific Technology Ltd. For the dust, quartz particles of 1 μm inparticle size were used and the measurement was carried out under acondition of the wind velocity of 8.6 cm/min at measurement.

Further, after 5 times washing in accordance with the method stipulatedin JIS L1096 B.23.1A, the dust collecting efficiency of the dried samplefabric was measured in a manner similar to that described above.

[Air Permeability (cc/cm²/sec.)]

The air permeability was measured with the use of the FRAZIER TYPE AIRPERMEABILITY TESTER (manufactured by and available from Toyo SeikiSeisaku-sho, Ltd.).

[Stretch of Protective Layer at Break (%)]

The stretch of protective layer at break was measured according to themethod stipulated in JIS P8113, with the use of an oblong test piece of1.5 cm in width.

[Tensile Strength (N/5 cm)]

The tensile strength was measured according to the method stipulated inJIS L1906, with the use of an oblong test piece of 5 cm in width.

Example 1

(1) Using crimped PVA fibers, which has a polymerization degree of1,750, saponification degree of 98.5 mole %, 2.2 dtex in single fiberfineness, 51 mm in fiber length and 5 cN/dtex in strength (tradenamed“WN7” manufactured by and available from Kuraray Co., Ltd.: 6% inshrinkage rate in 60° C. hot water, 65% shrinkage rate in 70° C. hotwater and dissolvable at 75° C.), a random web comprised of 100 parts bymass of the crimped PVA fibers and having a weight of 35 g/m² wasprepared.

(2) Then, a nonwoven fabric was produced with the web obtained under (1)above in the following manner, a so-called foam bonding process. Morespecifically, onto the web obtained under (1) above, was applied a foamprepared by beating a 10% aqueous solution of PVA which has apolymerization degree of 1,750 and a saponification degree of 98.5 mole% by a commercially available bubble machine. Then, the resultant webwas squeezed to spread the PVA resin foam uniformly over the web bymeans of a mangle, and the resultant was dried to obtain the nonwovenfabric. Thus obtained nonwoven fabric was used as a supporting layer. Itis to be noted that the rate of shrinkage of this supporting layer was15% in a hot water of 60° C. and 70% in a hot water of 70° C.

(3) On the other hand, the protective layer and the water resistantlayer were prepared in the following manner.

SEPTON (tradenamed under “SEPTON 2002” manufactured by and availablefrom Kuraray Co., Ltd.) and polypropylene (tradenamed under “NOVATEC PP”manufactured by and available from Japan Polychem Corporation) weremelted and kneaded together in a mixing ratio of 60/40 (mass ratio), andsubsequently a layer was formed by means of a meltblowing process toprovide a SEPTON/polypropylene blended nonwoven fabric having a weightof 10 g/m², which fabric was used as the protective layer.

Also, as the water resistant layer, a nonwoven fabric having a weight of20 g/m² was prepared by the meltblowing process, using polypropylene(tradenamed under “NOVATEC PP” manufactured by and available from JapanPolychem Corporation).

(4) Thereafter, the supporting layer, the protective layer and the waterresistant layer were overlapped one above the other in this specificorder, followed by bonding together by means of a calendering process(carried out under calendering conditions of 130° C. in temperature, 0.1MPa in contact pressure, and 5 m/min. in processing velocity) to therebyprovide a layered body having such a sectional structure as shown inFIG. 2. It is to be noted that in FIG. 2, A represents the supportinglayer, B represents the protective layer and C represents the waterresistant layer.

(5) The performance of the fabric consisting of the layered body, whichhas been manufactured in the manner described in (4), is shown inTable 1. The fabric so obtained was found to have a weight of 65 g/m², atensile strength of 120 N/5 cm×100 N/5 cm (MD direction×CD direction),an air permeability of 2.1 cc/cm²/sec., a 1 μm quartz dust collectingefficiency of 97.3%, and a 1 μm quartz dust collecting efficiency after5 times washing of 97.1%. The fabric was also found to have both of anair permeability and a filtering capability as the laminated fabric andto be excellent in integrity enough to exhibit the required filteringcapability even after it has been loaded by means of, for example,washing. Therefore, the laminated fabric has a performance sufficient toallow it to be used as a fabric for a protective clothing. Also, whenthe laminated fabric was immersed in a hot water of 60° C., 12%shrinkage occurred, and when it was immersed in a hot water of 70° C.,61% shrinkage occurred.

Example 2

(1) Using crimped PVA fibers of a kind, which has a polymerizationdegree of 1,750, a saponification degree of 98.5 mole %, 2.2 dtex insingle fiber fineness, 51 mm in fiber length and 5 cN/dtex in strength(tradenamed “WN7” manufactured by and available from Kuraray Co., Ltd.),a random web comprised of 100 parts by mass of the crimped PVA fibersand having a weight of 35 g/m² was prepared and was subsequentlysubjected to an embossing process to provide an embossed nonwovenfabric. The embossing process was carried out under conditions of 12% inthe ratio of embossing area, 180° C. in temperature, 40 kgf/cm in linepressure and 15 m/min. in processing velocity. This nonwoven fabric wasused as the supporting layer.

(2) On the other hand, the protective layer and the water resistantlayer were prepared in the following manner:

After placing polyurethane (tradenamed under “KURAMIRON 1190-000”manufactured by and available from Kuraray Co., Ltd.) in a vesselcontaining dimethylformamide (DMF) so that the concentration ofpolyurethane was 10 mass %, the mixture was agitated at 90° C. todissolve the polyurethane, and the completely dissolved solution wasthen cooled down to ambient temperatures to thereby provide a spinningliquid. Using the spinning liquid so prepared in the manner describedabove, an electrostatic spinning was carried out with the spinningapparatus shown in FIG. 1. For the spinnerets 4, needles each 0.9 mm indiameter were used. Also, the spinnerets 4 and the sheet take-upapparatus 7 were spaced at a distance of 12 cm from each other. It is tobe noted that in the sheet take-up apparatus 7, a polypropylene nonwovenfabric (the water resistant layer) having a weight of 20 g/m², which wasprepared from the polypropylene (tradenamed under “NOVATEC PP”manufactured by and available from Japan Polychem Corporation) in thesame way as in Example 1 by means of the meltblowing process, was woundbeforehand.

Thereafter, while the conveyor was driven at a velocity of 0.1 m/min.,the spinning liquid was extruded from the spinnerets in a predeterminedsupply rate, and a 25 kV voltage was applied to the spinnerets to form alaminate comprising a polyurethane nanofiber layer which had a weight of1.0 g/m² laminated over the water resistant layer which was pre-woundaround the sheet take-up apparatus 7.

(3) The supporting layer, prepared in the manner described in (1) above,and the protective layer and the water resistant layer, both prepared inthe manner described in (2) above, were overlapped with the protectivelayer forming an interlayer, and were then calendered in a mannersimilar to that described under Example 1 to thereby provide a layeredbody.

(4) The fabric prepared from this layered body was found to have aweight of 56 g/m², a tensile strength of 64 N/5 cm×54 N/5 cm (MDdirection×CD direction), an air permeability of 5.7 cc/cm²/sec., a 1 μmquartz dust collecting efficiency of 99.9%, and a 1 μm quartz dustcollecting efficiency after 5 times washing of 99.8%, as shown inTable 1. The fabric was also found to have both of an air permeabilityand a filtering capability as the laminated fabric and to be excellentin integrity enough to exhibit the required filtering capability evenafter it has been loaded by means of, for example, washing. For thereason discussed above, the laminated fabric has a performancesufficient to allow it to be used as a fabric for a protective clothing.Also, when the laminated fabric was immersed in a hot water of 60° C.,11% shrinkage occurred, and when it was immersed in a hot water of 70°C., 58% shrinkage occurred.

Example 3

(1) Using crimped PVA fibers of a kind, which has a polymerizationdegree of 1,750, a saponification degree of 98.5 mole %, 2.2 dtex insingle fiber fineness, 51 mm in fiber length and 5 cN/dtex in strength(tradenamed “WN7” manufactured by and available from Kuraray Co., Ltd.:6% in shrinkage rate in 60° C. hot water, 65% shrinkage rate in 70° C.hot water and dissolvable at 75° C.), a random web comprised of 100parts by mass of the crimped PVA fibers and having a weight of 35 g/m²was prepared.

(2) Then, a nonwoven fabric was produced with the web obtained under (1)above in the following manner, a so-called foam bonding process. Morespecifically, onto the web obtained under (1) above, was applied a foamprepared by beating a 10% aqueous solution of PVA which has apolymerization degree of 1,750 and a saponification degree of 98.5 mole% by a commercially available bubble machine. Then, the resultant webwas squeezed to spread the PVA resin foam uniformly over the web bymeans of a mangle, and the resultant was dried to obtain the nonwovenfabric. Thus obtained nonwoven fabric was used as a supporting layer. Itis to be noted that the rate of shrinkage of this supporting layer was15% in a hot water of 60° C. and 70% in a hot water of 70° C.

(3) For the water resistant layer, was prepared a polypropylene nonwovenfabric (water resistant layer) having a weight of 20 g/m², which wasprepared by the meltblowing process using the same polypropylene as thatused in Example 1 (“NOVATEC PP” tradenamed polypropylene manufactured byand available from Japan Polychem Corporation).

(4) Thereafter, while the supporting layer was moved at a conveyorvelocity of 50 m/min., a hot melt resin (tradenamed “INSTANTLOCK MP801”available from Nippon NSC Ltd.; melting point: about 140° C.) wasuniformly applied to the supporting layer in a quantity of 2 g/m² underconditions of 190° C. in nozzle temperature and 205° C. in hot airtemperature to form a resin coating on the supporting layer, followed bycooling the coating once and winding around a take-up roll. Also, in amanner similar to the supporting layer, the hot melt resin referred toabove was also applied to the water resistant layer referred to above ina quantity of 2 g/m².

(5) On the other hand, the protective layer was prepared in thefollowing manner.

After placing SEPTON (tradenamed under “SEPTON 2002” manufactured by andavailable from Kuraray Co., Ltd. and having a softening point of about150° C.) in a vessel containing dimethylformamide (DMF) so that theconcentration of SEPTON was 10 mass %, the mixture was agitated at 90°C. to dissolve the SEPTON, and the completely dissolved solution wasthen cooled down to ambient temperatures to thereby provide a spinningliquid. Using the spinning liquid so prepared in the manner describedabove, an electrostatic spinning was carried out with the spinningapparatus shown in FIG. 1. For the spinnerets 4, needles each 0.9 mm indiameter were used. Also, the spinnerets 4 and the sheet take-upapparatus 7 were spaced at a distance of 10 cm from each other. It is tobe noted that the sheet take-up apparatus 7 was surrounded by thesupporting layer coated with the hot melt resin which was obtained in(4) above, so that the surface of the hot melt resin was deposited withnanofibers.

Thereafter, while the conveyor was driven at a velocity of 0.1 m/min.,the spinning liquid was extruded from the spinnerets, to the spinneretsa 20 kV voltage was applied, in a predetermined supply rate to obtaindeposit or scaffold of 1.0 g/m² of SEPTON nanofibers over the waterresistant layer, and then the composite layer was wound around the sheettake-up apparatus 7.

(6) Further, the supporting layer, deposited with the SEPTON nanofiberlayer, and the water resistant layer, coated with the hot melt resin asin (4) above, were overlapped one above the other with the hot meltresin coating on the water resistant layer held in contact with theSEPTON nanofiber layer, and then were bonded together by means of acalendering process (carried out under calendering conditions of 140° C.in temperature, 0.1 MPa in contact pressure, and 5 m/sec. in processingvelocity) to thereby provide a layered body. The fabric prepared fromthis layered body was found to have a weight of 60 g/m², a tensilestrength of 93 N/5 cm×49 N/5 cm (MD direction×CD direction), an airpermeability of 8.1 cc/cm²/sec., a 1 μm quartz dust collectingefficiency of 99.7%, and a 1 μm quartz dust collecting efficiency after5 times washing of 99.7%, as shown in Table 1. The fabric was also foundto have both of an air permeability and a filtering capability as thelaminated fabric and to be excellent in integrity enough to exhibit therequired filtering capability even after it has been loaded by means of,for example, washing. Accordingly, the laminated fabric has aperformance sufficient to allow it to be used as a fabric for aprotective clothing. Also, when the laminated fabric was immersed in ahot water of 60° C., 12% shrinkage occurred, and when it was immersed ina hot water of 70° C., 64% shrinkage occurred.

Example 4

(1) A nylon spun bonded nonwoven fabric having a weight of 30 g/m²(tradenamed “ELTAS N01030” manufactured by and available from AsahiKasei Corporation) was used as the supporting layer.

(2) A polypropylene nonwoven fabric having a weight of 20 g/m² preparedfrom the same polypropylene (tradenamed “NOVATEC PP” manufactured by andavailable from Japan Polychem Corporation) as that used in Example 1 bymeans of the meltblowing process was used as the water resistant layer.

(3) Then, while the supporting layer was moved at a conveyor velocity of50 m/min., a hot melt resin (tradenamed “INSTANTLOCK MP801” availablefrom Nippon NSC Ltd.) was uniformly applied to the supporting layer in aquantity of 2 g/m² under conditions of 190° C. in nozzle temperature and205° C. in hot air temperature to form a resin coating on the supportinglayer, followed by cooling the coating once and winding around a take-uproll. Also, in a manner similar to the supporting layer, the hot meltresin referred to above was also applied to the water resistant layerreferred to above in a quantity of 2 g/m².

(4) On the other hand, the protective layer was prepared in thefollowing manner.

After placing polyurethane (tradenamed under “KURAMIRON 1190-000”manufactured by and available from Kuraray Co., Ltd.) in a vesselcontaining dimethylformamide (DMF) so that the concentration ofpolyurethane was 10 mass %, the mixture was agitated at 90° C. todissolve the polyurethane and the completely dissolved solution was thencooled down to ambient temperatures to thereby provide a spinningliquid. Using the spinning liquid so prepared in the manner describedabove, an electrostatic spinning was carried out with the spinningapparatus shown in FIG. 1. For the spinnerets 4, needles each 0.9 mm indiameter were used. Also, the spinnerets 4 and the sheet take-upapparatus 7 were spaced at a distance of 12 cm from each other. It is tobe noted that the sheet take-up apparatus 7 was surrounded by thesupporting layer coated with the hot melt resin which was obtained in(3) above, so that the surface of the hot melt resin was deposited withnanofibers.

Thereafter, while the conveyor was driven at a velocity of 0.1 m/min.,the spinning liquid was extruded from the spinnerets in a predeterminedsupply rate, and a 25 kV voltage was applied to the spinnerets tolaminate 1.0 g/m² of polyurethane nanofibers over the nonwoven layer.

(5) Further, the supporting layer, deposited with the polyurethanenanofiber layer, and the water resistant layer, coated with the hot meltresin as in (3) above, were overlapped one above the other with the hotmelt resin coating on the water resistant layer held in contact with thepolyurethane nanofiber layer, and then were bonded together by means ofa calendering process (carried out under calendering conditions of 140°C. in temperature, 0.1 MPa in contact pressure, and 5 m/sec. inprocessing velocity) to thereby provide a layered body. The fabricprepared from this layered body was found to have a weight of 55 g/m², atensile strength of 105 N/5 cm×71 N/5 cm (MD direction×CD direction), anair permeability of 8.4 cc/cm²/sec., a 1 μm quartz dust collectingefficiency of 99.9%, and a 1 μm quartz dust collecting efficiency after5 times washing of 99.8%, as shown in Table 1. The fabric was also foundto have both of an air permeability and a filtering capability as thelaminated fabric and to be excellent in integrity enough to exhibit therequired filtering capability even after it has been loaded by means of,for example, washing. Accordingly, the laminated fabric has aperformance sufficient to allow it to be used as a fabric for aprotective clothing.

Example 5

Except for using a polyethylene terephthalate spun bonded nonwovenfabric (tradenamed “ELTAS E01030” manufactured by and available fromAsahi Kasei Corporation) having a weight of 30 g/m² as the supportinglayer instead of the foam bonded PVA nonwoven fabric employed on thesupporting layer in Example 3, a fabric was prepared in a manner similarto that in Example 3. As shown in Table 1, the fabric so prepared wasfound to have a weight of 55 g/m², a tensile strength of 124 N/5 cm×77N/5 cm (MD direction×CD direction), an air permeability of 9.1cc/cm²/sec., a 1 μm quartz dust collecting efficiency of 99.6%, and a 1μm quartz dust collecting efficiency after 5 times washing of 99.5% andwas also found to have both of an air permeability and a filteringcapability as the laminated fabric and to be excellent in integrityenough to exhibit the required filtering capability even after it hasbeen loaded by means of, for example, washing.

Comparative Example 1

The polypropylene nonwoven fabric (the water resistant layer) and thenylon nonwoven fabric (the supporting layer) both obtained in (3) ofExample 4 and applied with the hot melt resin were directly overlappedone above the other with the hot melt resin adhering thereto, with noprotective layer intervening therebetween, and were subsequentlysubjected to a calendaring process in a manner similar to that inExample 4 to form a fabric. As shown in Table 1, this fabric was foundto have a weight of 54 g/m², a tensile strength of 101 N/5 cm×70 N/5 cm(MD direction×CD direction), an air permeability of 21 cc/cm²/sec., a 1μm quartz dust collecting efficiency of 33.1%, and a 1 μm quartz dustcollecting efficiency after 5 times washing of 32.8% and was also foundto have an unacceptable filtering capability.

Comparative Example 2

(1) A nylon spun bonded nonwoven fabric having a weight of 30 g/m²(tradenamed “ELTAS N01030” manufactured by and available from AsahiKasei Corporation) was used as the supporting layer.

(2) A polypropylene nonwoven fabric having a weight of 20 g/m² preparedfrom the same polypropylene (tradenamed “NOVATEC PP” manufactured by andavailable from Japan Polychem Corporation) as that used in Example 1 bymeans of the meltblowing process was used as the water resistant layer.

(3) Then, while the supporting layer was moved at a conveyor velocity of50 m/min., a hot melt resin (tradenamed “INSTANTLOCK MP801” availablefrom Nippon NSC Ltd.) was uniformly applied to the supporting layer in aquantity of 2 g/m² under conditions of 190° C. in nozzle temperature and205° C. in hot air temperature to form a resin coating on the supportinglayer, followed by cooling the coating once and winding around a take-uproll. Also, in a manner similar to the supporting layer, the hot meltresin referred to above was also applied to the water resistant layerreferred to above.

(4) On the other hand, the protective layer was prepared in thefollowing manner.

After placing polyacrylonitrile (manufactured by and available fromSigma Aldrich Co.; weight average molecular weight: 150,000) in a vesselcontaining dimethylformamide (DMF) so that the concentration ofpolyacrylonitrile is 11 mass %, the mixture was agitated at 90° C. todissolve the polyacrylonitrile and the completely dissolved solution wasthen cooled down to ambient temperatures to thereby provide a spinningliquid. Using the spinning liquid so prepared in the manner describedabove, an electrostatic spinning was carried out with the spinningapparatus shown in FIG. 1. For the spinnerets 4, needles each 0.9 mm indiameter were used. Also, the spinnerets 4 and the sheet take-upapparatus 7 were spaced at a distance of 10 cm from each other. It is tobe noted that the sheet take-up apparatus 7 was surrounded by thesupporting layer coated with the hot melt resin which was obtained in(3) above, so that the surface of the hot melt resin was deposited withnanofibers.

Thereafter, while the conveyor was driven at a velocity of 0.1 m/min.,the spinning liquid was extruded from the spinnerets in a predeterminedsupply rate, and a 18 kV voltage was applied to the spinnerets tolaminate 1.0 g/m² of polyacrylonitrile nanofibers over the nonwovenlayer.

(5) Also, the supporting layer, laminated with the polyacrylonitrilenanofiber layer, and the water resistant layer, coated with the hot meltresin as in (3) above, were overlapped one above the other with the hotmelt resin coating on the water resistant layer held in contact with thepolyacrylonitrile nanofiber layer and were bonded together by means of acalendering process (carried out under calendering conditions of 140° C.in temperature, 0.1 MPa in contact pressure, and 5 m/sec. in processingvelocity) to thereby provide a layered body. The fabric prepared fromthis layered body was found to have a weight of 55 g/m², a tensilestrength of 104 N/5 cm×70 N/5 cm (MD direction×CD direction), an airpermeability of 7.5 cc/cm²/sec., a 1 μm quartz dust collectingefficiency of 99.6%, and a 1 μm quartz dust collecting efficiency after5 times washing of 84.1%, as shown in Table 1. The fabric was also foundto have lost an integrity for the nonwoven fabric enough to fail tomaintain the required filtering capability.

Comparative Example 3

As a comparison, when the performance of a commercially available fabrictradenamed “TYVEK SOFT” (having a weight of 41 g/m²) and manufactured byand available from E. I. du Pont de Nemours and Company, which iscurrently used as the standard protective base material, was evaluated,the tensile strength thereof was found to be 80 N/5 cm×94 N/5 cm (MDdirection×CD direction) and the 1 μm quartz dust collecting efficiencywas found to be so high as 98.5% as shown in Table 1. However, the airpermeability of the commercially available fabric referred to above wasfound to be very low of 0.4 cc/cm²/sec. and no shrinkage was foundoccurring in a hot water of either 60° C. and 70° C.

TABLE 1 Com. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Com. Ex. 1 Com. Ex. 2 Ex. 3Supporting Material PVA PVA PVA Nylon PET Nylon Nylon “TYVEK Layer FormFoambond Emboss Foambond Spunbond Spunbond Spunbond Spunbond SOFT”Weight(g/m²) 35 35 35 30 30 30 30 Protective Material SEPTON/PPPolyurethane SEPTON Polyurethane SEPTON — PAN Layer Form MeltblowingNanofiber Nanofiber Nanofiber Nanofiber — Nanofiber Weight(g/m²) 10 1 11 1 — 1 Stretch at 205 51 38 51 38 — 24 break (%) Water Material PP PPPP PP PP PP PP Resistant Form MB MB MB MB MB MB MB Layer Weight(g/m²) 2020 20 20 20 20 20 Adhering Method Calender Calender Hot melt Hot meltHot melt Hot melt Hot melt Total Weight 65 56 60 55 55 54 55 41 TensileMD 120 64 93 105 124 101 104 80 Strength CD 100 54 49 71 77 70 70 94(N/5 cm) Air Permeability 2.1 5.7 8.1 8.4 9.1 21 7.5 0.4 (cc/cm²/sec)Collecting Before 97.3 99.9 99.7 99.7 99.6 33.1 99.6 98.5 EfficiencyWashing After 5 times 97.1 99.8 99.7 99.8 99.5 32.8 84.1 98.3 WashingWithstanding 1132 850 753 811 781 751 831 1005 Pressure (mmH₂O)Shrinkage 60° C. water 12 11 12 0 0 0 0 0 Rate (%) 70° C. water 61 58 640 0 0 0 0

The laminated fabric of the present invention is advantageously used asa protective material for protecting human bodies from harmful and/orhazardous substances such as, for example, dust harmful to human bodies,contagions and viruses, and/or harmful and/or hazardous substancesafloat in the atmospheric air. Such protective material is used not onlyas a protective clothing (such as, for example, protective clothes,masks, gloves and/or hats), but also sheeting, protectors and/or filtersof a kind used under the environment, where the harmful and/or hazardoussubstances tend to stick thereto, to protect human bodies from thesecondary infection of those harmful and/or hazardous substances.

Also, where the laminated fabric has a volume reducing capability, sincethe laminated fabric (or the protective material) can be reduced involume and be then transported or disposed of after use, the costincurred in transportation or disposal can be reduced advantageously.

1. A laminated fabric which comprises: a supporting layer; and aprotective layer comprising a stretchable nonwoven fabric formed from anultra-fine fiber, the protective layer bonded to the supporting layer;whereby the laminated fabric having an air permeability of 2 cc/cm²/secor higher and also having an efficiency of 90% or higher when collectingquartz particles 1 μm in size.
 2. The laminated fabric as claimed inclaim 1, in which the ultra-fine fiber comprises a thermoplasticelastomer.
 3. The laminated fabric as claimed in claim 2, in which thethermoplastic elastomer comprises at least one thermoplastic elastomerselected from the group consisting of SEPS, SEBS, a polyurethane seriesthermoplastic elastomer, a polyester series thermoplastic elastomer anda polyamide series thermoplastic elastomer.
 4. The laminated fabric asclaimed in claim 1, in which the stretchable nonwoven fabric has astretch of 30% or higher at break.
 5. The laminated fabric as claimed inclaim 1, in which the stretchable nonwoven fabric comprises anultra-fine fiber being a nanofiber of 10 to 1,000 nm in fiber diameterand also have a weight within the range of 0.01 to 10 g/m².
 6. Thelaminated fabric as claimed in claim 1, in which at least a part of thefibers forming the supporting layer is a volume reducible fiber.
 7. Thelaminated fabric as claimed in claim 6, in which the volume reduciblefiber comprises a polyvinyl alcohol fiber.
 8. The laminated fabric asclaimed in claim 1, further comprising a water resistant layer, thewater resistant layer being positioned on the protective layer so thatthe protective layer is employed as an intermediate layer between thewater resistant layer and the supporting layer.
 9. The laminated fabricas claimed in claim 8, which has a withstanding pressure within therange of 300 to 1,500 mmH₂O.
 10. The laminated fabric as claimed inclaim 1, in which 5 to 90% shrinkage takes place when immersed in a hotwater of 60° C. or higher.
 11. A protective material, in which at leasta part thereof comprises a laminated fabric as defined in claim
 1. 12. Avolume reducing method which comprises placing a laminated fabric asdefined in claim 1 into a sealable vessel and supplying a hot water of60° C. or higher to the laminated fabric.